Anich et al. • KIRTLAND'S WARBLERS IN RED PINE 
203 
FIG. 2. Height of the lowest live branch on trees in stands used by Kirtland's Warblers. White bars are means of all 
trees at 11 wildfire sites and 10 (jack pine) plantation sites in Michigan measured by Bocetti (1994). Gray bars are from 160 
trees measured at a used site in Adams County, Wisconsin, and include 107 red pine, 33 northern pin oak/black oak, and 21 
jack pine. Error bars are 95% confidence intervals. 
plantation sites provides more cover with fewer 
trees than in naturally regenerated sites (Probst 
1988). 
Tree height can provide some measure of the 
stage of a Kirtland’s Warbler stand (Probst and 
Weinrich (1993). Our population was not moni¬ 
tored before 2007: we do not know how long birds 
were present at the site and whether our site is just 
becoming occupied, is in its prime, or is declining. 
Average heights of jack pines in our study have 
been typically associated with declining stands 
(Probst and Weinrich 1993) but red pine-domi¬ 
nated stands may have a different succession 
scenario. The stand in our study, based on tree 
canopy cover which increases with stand age. may 
be in its prime condition for nesting warblers 
(Probst and Weinrich 1993). 
The persistence of low live branches in our 
stand supports the view that low branch density is 
an important characteristic of suitable Kirtland's 
Warbler habitat; several authors (Mayfield 1960. 
Probst 1988. Probst and Weinrich 1993) have 
suggested low live branches are critical for 
nesting, female foraging, and nestling cover. We 
frequently observed females and recently fledged 
young using low branches for foraging and cover, 
and we found four nests directly beneath very low 
live red pine branches. The extremely low mean 
live green branch height shown by red pine at our 
site may indicate one reason for the settlement of 
our site by Kirtland’s Warblers. A red pine 
component to a stand might prolong use of that 
stand by Kirtland’s Warblers if loss of live green 
branches is a main reason for abandonment of a 
stand (Probst 1988). 
Ground cover types at our site were comparable 
to other sites, although our site was more 
dominated by sedges dian most Kirtland’s War¬ 
bler sites (Bocetti 1994. Houseman and Anderson 
2002. Probst and Donnerwright 2003). Some 
plants commonly observed in Michigan were not 
common at our site: bearberry (Arctostaphylos 
uva-ursi) and sand cherry (Primus putnila) were 
present but not common, and we observed no 
sweet fem (Comptonia peregrina). The domi¬ 
nance of sedges and relative Jack of forbs and 
grasses at our site may be related to application of 
herbicide during site preparation, although others 
